Cooling system

ABSTRACT

A cooling system ( 1 ) includes: a compressor ( 12 ) that circulates refrigerant; a heat exchanger ( 14 ) and a heat exchanger ( 15 ) that carry out heat exchange between refrigerant and outside air; a decompressor ( 16 ) that decompresses refrigerant; a heat exchanger ( 18 ) that carries out heat exchange between refrigerant and air-conditioning air; a cooling portion ( 30 ) that is provided in a path of refrigerant flowing between the heat exchanger ( 14 ) and the heat exchanger ( 15 ) and that uses refrigerant to cool a heat generating source ( 31 ); a first line ( 24 ) through which refrigerant circulates between the cooling portion ( 30 ) and the heat exchanger ( 15 ); a second line ( 27 ) through which refrigerant circulates between the heat exchanger ( 18 ) and the compressor ( 12 ); and an internal heat exchanger ( 40 ) in which refrigerant that circulates through the first line ( 24 ) and refrigerant that circulates through the second line ( 27 ) exchange heat with each other.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a cooling system and, more particularly, to acooling system that utilizes a vapor compression refrigeration cycle tocool a heat generating source.

2. Description of Related Art

In recent years, hybrid vehicles, fuel cell vehicles, electric vehicles,and the like, that run using driving force of a motor become a focus ofattention as one of measures against environmental issues. In suchvehicles, electrical devices, such as a motor, a generator, an inverter,a converter and a battery, exchange electric power to generate heat.Therefore, these electrical devices need to be cooled. Then, there hasbeen suggested a technique that utilizes a vapor compressionrefrigeration cycle, which is used as a vehicle air conditioner, to coola heat generating element.

For example, Japanese Patent Application Publication No. 2006-290254 (JP2006-290254 A) describes a cooling system for a hybrid vehicle. Thecooling system includes: a compressor that is able to introduce andcompress gaseous refrigerant; a main condenser that is able to coolhigh-pressure gaseous refrigerant using ambient air to condense thehigh-pressure gaseous refrigerant; an evaporator that is able toevaporate low-temperature liquid refrigerant to cool an refrigeratingobject; and a decompressing unit, and a heat exchanger, which is able toabsorb heat from a motor, and a second decompressing unit are connectedin parallel with the decompressing unit and the evaporator. JapanesePatent Application Publication No. 2007-69733 (JP 2007-69733 A)describes a system in which a heat exchanger that exchanges heat withair-conditioning air and a heat exchanger that exchanges heat with aheat generating element are arranged in parallel with each other in arefrigerant line routed from an expansion valve to a compressor andrefrigerant for an air conditioner is utilized to cool the heatgenerating element.

Japanese Patent Application Publication No. 2005-90862 (JP 2005-90862 A)describes a cooling system in which a heat generating element coolingunit for cooling a heat generating element is provided in a bypass linethat bypasses the decompressor, evaporator and compressor of anair-conditioning refrigeration cycle. Japanese Patent ApplicationPublication No. 2001-309506 (JP 2001-309506 A) describes a coolingsystem that circulates refrigerant of a vehicle air-conditioningrefrigeration cycle through a cooling member of an inverter circuitportion that executes drive control over a vehicle drive motor and, whencooling air-conditioning air stream is not required, cooling ofair-conditioning air stream by an evaporator of the vehicleair-conditioning refrigeration cycle is suppressed.

In the cooling system described in JP 2006-290254 A, in order to cool aheat generating source, such as electrical devices that are typically amotor, a DC/DC converter and an inverter, it is necessary to constantlyoperate the compressor. Therefore, there is a problem that the powerconsumption of the compressor increases and the fuel economy of thevehicle deteriorates. In addition, the heat exchanger that exchangesheat with the heat generating source is connected in parallel with theevaporator, so refrigerant for cooling the heat generating source is notused for cooling, and there is a problem that cooling performance istraded off.

SUMMARY OF THE INVENTION

The invention provides a cooling system that is able to reliably cool aheat generating source while ensuring cooling performance, and that isable to reduce the power consumption of a compressor.

An aspect of the invention relates to a cooling system that cools a heatgenerating source. The cooling system includes: a compressor thatcirculates refrigerant; a first heat exchanger and a second heatexchanger that carry out heat exchange between the refrigerant andoutside air; a decompressor that decompresses the refrigerant; a thirdheat exchanger that carries out heat exchange between the refrigerantand air-conditioning air; a cooling portion that is provided in a pathof the refrigerant flowing between the first heat exchanger and thesecond heat exchanger and that uses the refrigerant to cool the heatgenerating source; a first line through which the refrigerant flowsbetween the cooling portion and the second heat exchanger; a second linethrough which the refrigerant flows between the third heat exchanger andthe compressor; and an internal heat exchanger in which the refrigerantthat flows through the first line and the refrigerant that flows throughthe second line exchange heat with each other.

In the cooling system, the internal heat exchanger may be arrangedbetween the cooling portion and the second heat exchanger.

The cooling system may further include: a third line through which therefrigerant flows between the compressor and the first heat exchanger;and a fourth line that provides fluid communication between the firstline and the third line. The cooling system may further include aselector valve that switches a state of fluid communication between thefourth line and the first line and third line. In the cooling system,the selector valve may be configured so as to switch the state of fluidcommunication into a state where the refrigerant flows through thefourth line during a stop of the compressor. In the cooling system, thecooling portion may be arranged below the first heat exchanger.

The cooling system may further include a four-way valve that switchesbetween flow of the refrigerant from the compressor toward the firstheat exchanger and flow of the refrigerant from the compressor towardthe third heat exchanger.

In the cooling system, the first heat exchanger and the second heatexchanger may be integrally arranged.

With the cooling system according to the aspect of the invention, it ispossible to reliably cool a heat generating source while ensuringcooling performance, and it is possible to reduce the power consumptionof a compressor.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments of the invention will be described below withreference to the accompanying drawings, in which like numerals denotelike elements, and wherein:

FIG 1 is a schematic view that shows the configuration of a coolingsystem according to a first embodiment of the invention;

FIG. 2 is a Mollier chart that shows the state of refrigerant duringcooling operation of a vapor compression refrigeration cycle accordingto the first embodiment of the invention;

FIG. 3A to FIG. 3D are graphs that schematically show opening degreecontrol over a flow regulating valve;

FIG. 4 is a schematic view that shows the cooling system in a statewhere a four-way valve is switched;

FIG. 5 is a Mollier chart that shows the state of refrigerant duringheating operation of a vapor compression refrigeration cycle accordingto the first embodiment of the invention;

FIG. 6 is a schematic view that shows the flow of refrigerant that coolsan HV device during operation of the vapor compression refrigerationcycle;

FIG. 7 is a schematic view that shows the flow of refrigerant that coolsthe HV device during a stop of the vapor compression refrigerationcycle;

FIG. 8 is a schematic view that shows the configuration of a coolingsystem according to a second embodiment of the invention; and

FIG. 9 is a schematic view that shows an example of the internalstructure of a heat exchanger according to the second embodiment Of theinvention.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the invention will be described withreference to the accompanying drawings. Note that, in the followingdrawings, like reference numerals denote the same or correspondingportions and the description thereof is not repeated.

First Embodiment

FIG. 1 is a schematic view that shows the configuration of a coolingsystem 1 according to a first embodiment. As shown in FIG. 1, thecooling system 1 includes a vapor compression refrigeration cycle 10.The vapor compression refrigeration cycle 10 is, for example, mounted ona vehicle in order to cool or heat the cabin of the vehicle. Coolingusing the vapor compression refrigeration cycle 10 is performed, forexample, when a switch for cooling is turned on or when an automaticcontrol mode in which the temperature in the cabin of the vehicle isautomatically adjusted to a set temperature is selected and thetemperature in the cabin is higher than the set temperature. Heatingusing the vapor compression refrigeration cycle 10 is performed, forexample, when a switch for heating is turned on or when the automaticcontrol mode is selected and the temperature in the cabin is lower thanthe set temperature.

The vapor compression refrigeration cycle 10 includes a compressor 12, aheat exchanger 14 that serves as a first heat exchanger, a heatexchanger 15 that serves as a second heat exchanger, an expansion valve16 that is an example of a decompressor, and a heat exchanger 18 thatserves as a third heat exchanger. The vapor compression refrigerationcycle 10 further includes a four-way valve 13. The four-way valve 13 isarranged so as to be able to switch between flow of refrigerant from thecompressor 12 toward the heat exchanger 14 and flow of refrigerant fromthe compressor 12 toward the heat exchanger 18.

The compressor 12 is actuated by a motor or engine equipped for thevehicle as a power source, and adiabatically compresses refrigerant gasto obtain superheated refrigerant gas. The compressor 12 introduces andcompresses gaseous refrigerant flowing during operation of the vaporcompression refrigeration cycle 10, and discharges high-temperature andhigh-pressure gaseous refrigerant. The compressor 12 dischargesrefrigerant to circulate the refrigerant in the vapor compressionrefrigeration cycle 10.

Each of the heat exchangers 14, 15 and 18 includes tubes and fins. Thetubes flow refrigerant. The fins are used to exchange heat betweenrefrigerant flowing through the tubes and air around the heat exchanger14, 15 or 18. Each of the heat exchangers 14, 15 and 18 exchanges heatbetween refrigerant and air stream supplied by natural draft generatedas the vehicle runs or air stream supplied by a fan.

The expansion valve 16 causes high-pressure liquid refrigerant to besprayed through a small hole to expand into low-temperature andlow-pressure atomized refrigerant. The expansion valve 16 decompressescondensed refrigerant liquid into wet steam in a gas-liquid mixingstate. Note that a decompressor for decompressing refrigerant liquid isnot limited to the expansion valve 16 that carries out throttleexpansion; instead, the decompressor may be a capillary tube.

The vapor compression refrigeration cycle 10 further includesrefrigerant lines 21 to 28. The refrigerant line 21 provides fluidcommunication between the compressor 12 and the four-way valve 13.Refrigerant flows from the compressor 12 toward the four-way valve 13via the refrigerant line 21. The refrigerant line 22 provides fluidcommunication between the four-way valve 13 and the heat exchanger 14.Refrigerant flows from one of the four-way valve 13 and the heatexchanger 14 toward the other via the refrigerant line 22. Therefrigerant line 23 provides fluid communication between the heatexchanger 14 and a cooling portion 30 (described later). Refrigerantflows from one of the heat exchanger 14 and the cooling portion 30toward the other via the refrigerant line 23. The refrigerant line 24provides fluid communication between the cooling portion 30 and the heatexchanger 15. Refrigerant flows from one of the cooling portion 30 andthe heat exchanger 15 toward the other via the refrigerant line 24.

The refrigerant line 25 provides fluid communication between the heatexchanger 15 and the expansion valve 16. Refrigerant flows from one ofthe heat exchanger 15 and the expansion valve 16 toward the other viathe refrigerant line 25. The refrigerant line 26 provides fluidcommunication between the expansion valve 16 and the heat exchanger 18.Refrigerant flows from one of the expansion valve 16 and the heatexchanger 18 toward the other via the refrigerant line 26. Therefrigerant line 27 provides fluid communication between the heatexchanger 18 and the four-way valve 13. Refrigerant flows from one ofthe heat exchanger 18 and the four-way valve 13 toward the other via therefrigerant line 27. The refrigerant line 28 provides fluidcommunication between the four-way valve 13 and the compressor 12.Refrigerant flows from the four-way valve 13 toward the compressor 12via the refrigerant line 28.

The vapor compression refrigeration cycle 10 is formed such that thecompressor 12, the heat exchangers 14 and 15, the expansion valve 16 andthe heat exchanger 18 are coupled by the refrigerant lines 21 to 28.Note that refrigerant used in the vapor compression refrigeration cycle10 may be, for example, carbon dioxide, hydrocarbon, such as propane andisobutane, ammonia, water, or the like.

The cooling portion 30 is provided in the path of refrigerant flowingbetween the heat exchanger 14 and the heat exchanger 15. Because thecooling portion 30 is provided, the path of refrigerant between the heatexchanger 14 and the heat exchanger 15 is divided into the refrigerantline 23 closer to the heat exchanger 14 than the cooling portion 30 andthe refrigerant line 24 closer to the expansion valve 16 than thecooling portion 30. The cooling portion 30 includes a hybrid vehicle(HV) device 31 and a cooling line 32. The HV device 31 is an electricaldevice mounted on the vehicle. The cooling line 32 is a line throughwhich refrigerant flows. The HV device 31 is an example of a heatgenerating source. One end portion of the cooling line 32 is connectedto the refrigerant line 23. The other end portion of the cooling line 32is connected to the refrigerant line 24.

Refrigerant flowing between the heat exchanger 14 and the expansionvalve 16 flows via the cooling line 32. When refrigerant flows throughthe cooling line 32, the refrigerant takes heat from the HV device 31 tocool the HV device 31. The cooling portion 30 is configured to be ableto exchange heat between the HV device 31 and refrigerant because of thecooling line 32. In the present embodiment, the cooling portion 30, forexample, has the cooling line 32 that is formed such that the outerperipheral surface of the cooling line 32 is in direct contact with thecasing of the HV device 31. The cooling line 32 has a portion adjacentto the casing of the HV device 31. At that portion, heat is exchangeablebetween refrigerant, flowing through the cooling line 32, and the HVdevice 31.

The HV device 31 is directly connected to the outer peripheral surfaceof the cooling line 32 that forms part of the path of refrigerant,routed from the heat exchanger 14 to the heat exchanger 15 in the vaporcompression refrigeration cycle 10, and is cooled. The HV device 31 isarranged on the outside of the cooling line 32, so the HV device 31 doesnot interfere with flow of refrigerant flowing inside the cooling line32. Therefore, the pressure loss of the vapor compression refrigerationcycle 10 does not increase, so the HV device 31 may be cooled withoutincreasing the power of the compressor 12.

Alternatively, the cooling portion 30 may include a selected known heatpipe that is interposed between the HV device 31 and the cooling line32. In this case, the HV device 31 is connected to the outer peripheralsurface of the cooling line 32 via the heat pipe, and heat istransferred from the HV device 31 to the cooling line 32 via the heatpipe to thereby cool the HV device 31. The HV device 31 serves as aheating portion for heating the heat pipe, and the cooling line 32serves as a cooling portion for cooling the heat pipe to therebyincrease the heat-transfer efficiency between the cooling line 32 andthe HV device 31, so the cooling efficiency of the HV device 31 may beimproved. For example, a Wick heat pipe may be used.

Heat may be reliably transferred from the HV device 31 to the coolingline 32 by the heat pipe, so there may be a distance between the HVdevice 31 and the cooling line 32, and complex arrangement of thecooling line 32 is not required to bring the cooling line 32 intocontact with the HV device 31. As a result, it is possible to improvethe flexibility of arrangement of the HV device 31.

The HV device 31 includes an electrical device that exchanges electricpower to generate heat. The electrical device includes at least any oneof, for example, an inverter used to convert direct-current power toalternating-current power, a motor generator that is a rotatingelectrical machine, a battery that is an electrical storage device, aconverter that is used to step up the voltage of the battery and a DC/DCconverter that is used to step down the voltage of the battery. Thebattery is a secondary battery, such as a lithium ion battery and anickel metal hydride battery. A capacitor may be used instead of thebattery.

The heat exchanger 18 is arranged inside a duct 90 through which airflows. The heat exchanger 18 exchanges heat between refrigerant andair-conditioning air flowing through the duct 90 to adjust thetemperature of air-conditioning air. The duct 90 has a duct inlet 91 anda duct outlet 92. The duct inlet 91 is an inlet through whichair-conditioning air flows into the duct 90. The duct outlet 92 is anoutlet through which air-conditioning air flows out from the duct 90. Afan 93 is arranged near the duct inlet 91 inside the duct 90.

As the fan 93 is driven, air flows through the duct 90. As the fan 93operates, air-conditioning air flows into the duct 90 via the duct inlet91. Air flowing into the duct 90 may be outside air or may be air in thecabin of the vehicle. The arrow 95 in FIG. 1 and FIG. 4 indicates flowof air-conditioning air that flows via the heat exchanger 18 andexchanges heat with refrigerant in the vapor compression refrigerationcycle 10. During cooling operation, air-conditioning air is cooled inthe heat exchanger 18, and refrigerant receives heat transferred fromair-conditioning air to be heated. During heating operation,air-conditioning air is heated in the heat exchanger 18, and refrigeranttransfers heat to air-conditioning air to be cooled. The arrow 96indicates flow of air-conditioning air that is adjusted in temperatureby the heat exchanger 18 and that flows out from the duct 90 via theduct outlet 92.

Refrigerant that flows through the refrigerant line 24 as a first linebetween the cooling portion 30 and the heat exchanger 15 and refrigerantthat flows through the refrigerant line 27 as a second line between theheat exchanger 18 and the four-way valve 13 exchange heat with eachother in an internal heat exchanger 40. The cooling system 1 includesthe internal heat exchanger 40 in which refrigerant that flows throughthe refrigerant line 24 and refrigerant that flows through therefrigerant line 27 exchange heat with each other. Because the internalheat exchanger 40 is provided, the refrigerant line 24 is divided into arefrigerant line 24 a closer to the cooling portion 30 than the internalheat exchanger 40 and a refrigerant line 24 b closer to the heatexchanger 15 than the Internal heat exchanger 40. The refrigerant line27 is divided into a refrigerant line 27 a closer to the heat exchanger18 than the internal heat exchanger 40 and a refrigerant line 27 bcloser to the four-way valve 13 than the internal heat exchanger 40.

The internal heat exchanger 40 has a heat exchanging line 41 that is influid communication with the refrigerant line 24 and a heat exchangingline 42 that is in fluid communication with the refrigerant line 27. Oneend portion of the heat exchanging line 41 is connected to therefrigerant line 24 a, and the other end portion is connected to therefrigerant line 24 b. During cooling operation shown in FIG. 1,refrigerant flows from the cooling portion 30 to the internal heatexchanger 40 via the refrigerant line 24 a, flows in the heat exchangingline 41, and reaches the heat exchanger 15 via the refrigerant line 24b. One end portion of the heat exchanging line 42 is connected to therefrigerant line 27 a, and the other end portion is connected to therefrigerant line 27 b. During cooling operation shown in FIG. 1,refrigerant flows from the heat exchanger 18 to the internal heatexchanger 40 via the refrigerant line 27 a, flows in the heat exchangingline 42, reaches the four-way valve 13 via the refrigerant line 27 b,and further flows into the compressor 12 via the refrigerant line 28.

The internal heat exchanger 40 has a selected structure such that heatis exchangeable between refrigerant that flows through the heatexchanging line 41 and refrigerant that flows through the heatexchanging line 42. For example, a pipe that forms the heat exchangingline 41 and a pipe that forms the heat exchanging line 42 may bearranged such that the respective outer peripheral surfaces directlycontact with each other or may be arranged via a high thermal conductivemember or a heat pipe. In addition, for example, it is applicable thattwo through holes are formed in a metal block member having a highthermal conductivity, one of the through holes serves as the heatexchanging line 41 and the other one of the through holes serves as theheat exchanging line 42.

During cooling operation, refrigerant flows in the vapor compressionrefrigeration cycle 10 so as to sequentially pass through points A, B,C, D, E, F, G and H shown in FIG. 1, and refrigerant circulates amongthe compressor 12, the heat exchangers 14 and 15, the expansion valve 16and the heat exchanger 18. Refrigerant passes through a refrigerantcirculation path that is formed by sequentially connecting the ,compressor 12, the heat exchangers 14 and 15, the expansion valve 16 andthe heat exchanger 18 by the refrigerant lines 21 to 28 to circulate inthe vapor compression refrigeration cycle 10.

FIG. 2 is a Mollier chart that shows the state of refrigerant duringcooling operation of the vapor compression refrigeration cycle 10according to the first embodiment. In FIG. 2, the abscissa axisrepresents the specific enthalpy (unit: kJ/kg) of refrigerant, and theordinate axis represents the absolute pressure (unit: MPa) ofrefrigerant. The curve in the chart is the saturation vapor line andsaturation liquid line of refrigerant. FIG. 2 shows the thermodynamicstate of refrigerant at points (that is, points A, B, C, D, E, F, G andH) in the vapor compression refrigeration cycle 10 when refrigerantflows from the compressor 12 into the refrigerant line 23 via the heatexchanger 14, cools the HV device 31 and returns from the refrigerantline 24 to the compressor 12 via the heat exchanger 15, the expansionvalve 16 and the heat exchanger 18.

As shown in FIG. 2, refrigerant (point A) in a superheated steam state,introduced into the compressor 12, is adiabatically compressed in thecompressor 12 along a constant specific entropy line. As refrigerant iscompressed, the refrigerant increases in pressure and temperature intohigh-temperature and high-pressure superheated steam having a highdegree of superheat (point B), and then the refrigerant flows to theheat exchanger 14.

High-pressure refrigerant steam flowing into the heat exchanger 14exchanges heat with outside air in the heat exchanger 14 to be cooled.Refrigerant becomes dry saturated steam from superheated steam with aconstant pressure, releases latent heat of condensation to graduallyliquefy into wet steam in a gas-liquid mixing state, and becomessaturated liquid as the entire refrigerant condenses (point C). The heatexchanger 14 causes superheated refrigerant gas, compressed in thecompressor 12, to release heat to an external medium with a constantpressure and to become refrigerant liquid. Gaseous refrigerantdischarged from the compressor 12 releases heat to the surroundings tobe cooled in the heat exchanger 14 to thereby condense (liquefy). Owingto heat exchange in the heat exchanger 14, the temperature ofrefrigerant decreases, and refrigerant liquefies.

High-pressure liquid refrigerant liquefied in the heat exchanger 14flows to the cooling portion 30 via the refrigerant line 23, and coolsthe HV device 31. In the cooling portion 30, heat is released to liquidrefrigerant that is condensed as it passes through the heat exchanger 14to thereby cool the HV device 31. Refrigerant is heated by exchangingheat with the HV device 31, and the dryness of the refrigerantincreases. Refrigerant receives latent heat from the HV device 31 topartially vaporize into wet steam that mixedly contains saturated liquidand saturated steam (point D).

Refrigerant flowing out from the cooling portion 30 flows to theinternal heat exchanger 40 via the refrigerant line 24 a. As heat istransferred from refrigerant that flows through the heat exchanging line41 to refrigerant that flows through the heat exchanging line 42 insidethe internal heat exchanger 40, refrigerant that flows through the heatexchanging line 41 is cooled, and refrigerant that flows through theheat exchanging line 42 is heated. The percentage of saturated liquidincreases and the percentage of saturated steam reduces withinrefrigerant that flows through the heat exchanging line 41 by heatexchange in the internal heat exchanger 40, so the dryness of therefrigerant in a wet steam state, flowing through the heat exchangingline 41, reduces (the wetness increases) (point E).

After that, refrigerant flows into the heat exchanger 15. Wet steam ofrefrigerant exchanges heat with outside air in the heat exchanger 15 tobe cooled to thereby condense again, becomes saturated liquid as theentire refrigerant condenses, and further releases sensible heat tobecome supercooled liquid (point F). After that, refrigerant flows intothe expansion valve 16 via the refrigerant line 25. In the expansionvalve 16, refrigerant in a supercooled liquid state isthrottle-expanded, and the refrigerant decreases in temperature andpressure with the specific enthalpy of the refrigerant unchanged tobecome low-temperature and low-pressure wet steam in a gas-liquid mixingstate (point G).

Refrigerant in a wet steam state from the expansion valve 16 flows intothe heat exchanger 18 via the refrigerant line 26. Refrigerant in a wetsteam state flows into the tubes of the heat exchanger 18. Whenrefrigerant flows through the tubes of the heat exchanger 18, therefrigerant absorbs heat of air in the cabin of the vehicle as latentheat of vaporization via the fins to evaporate with a constant pressure.As the entire refrigerant becomes dry saturated steam, the temperatureof refrigerant steam further increases by sensible heat to becomesuperheated steam (point H). Refrigerant absorbs heat from thesurroundings in the heat exchanger 18 to be heated.

Refrigerant flowing out from the heat exchanger 18 flows to the internalheat exchanger 40 via the refrigerant line 27 a and flows through theheat exchanging line 42. By the above described heat exchange in theinternal heat exchanger 40, refrigerant that flows through the heatexchanging line 42 is heated, and a degree of superheat of therefrigerant in a superheated steam state, flowing through the heatexchanging line 42, increases (point A). After that, refrigerant isintroduced into the compressor 12 via the refrigerant line 27 b, thefour-way valve 13 and the refrigerant line 28. The compressor 12compresses refrigerant that flows from the internal heat exchanger 40.Refrigerant continuously repeats changes among the compressed state, thecondensed state, the throttle-expanded state and the evaporated state inaccordance with the above described cycle.

Note that, in the above description of the vapor compressionrefrigeration cycle, a theoretical refrigeration cycle is described;however, in the actual vapor compression refrigeration cycle 10, it is,of course, necessary to consider a loss in the compressor 12, a pressureloss of refrigerant and a heat loss.

During cooling operation, atomized refrigerant flowing inside the heatexchanger 18 vaporizes to absorb heat of ambient air introduced so as tocontact with the heat exchanger 18. The heat exchanger 18 useslow-temperature and low-pressure refrigerant decompressed by theexpansion valve 16 to absorb heat of vaporization, required at the timewhen wet steam of refrigerant evaporates into refrigerant gas, fromair-conditioning air flowing to the cabin of the vehicle to thereby coolthe cabin of the vehicle. Air-conditioning air of which heat is absorbedby the heat exchanger 18 to decrease its temperature flows into thecabin of the vehicle to cool the cabin of the vehicle.

During operation of the vapor compression refrigeration cycle 10,refrigerant absorbs heat of vaporization from air in the cabin of thevehicle in the heat exchanger 18 to thereby cool the cabin. In addition,high-pressure liquid refrigerant from the heat exchanger 14 flows to thecooling portion 30 and exchanges heat with the HV device 31 to therebycool the HV device 31. The cooling system 1 cools the HV device 31,which is the heat generating source mounted on the vehicle, by utilizingthe vapor compression refrigeration cycle 10 for air-conditioning thecabin of the vehicle. Note that the temperature required to cool the HVdevice 31 is desirably at least lower than the upper limit of a targettemperature range of the HV device 31.

During cooling operation, refrigerant is cooled into a saturated liquidstate in the heat exchanger 14, and refrigerant in a wet steam state,which receives latent heat of vaporization from the HV device 31 to bepartially vaporized, is cooled again in the heat exchanger 15.Refrigerant changes in state at a constant temperature until therefrigerant in a wet steam state completely condenses into saturatedliquid. The heat exchanger 15 further supercools liquid refrigerant to adegree of supercooling required to cool the cabin of the vehicle. Adegree of supercooling of refrigerant does not need to be excessivelyincreased, so the capacity of each of the heat exchangers 14 and 15 maybe reduced. Thus, the cooling performance for cooling the cabin may beensured, and the size of each of the heat exchangers 14 and 15 may bereduced, so it is possible to obtain the cooling system 1 that isreduced in size and that is advantageous in installation on the vehicle.

When low-temperature and low-pressure refrigerant after passing throughthe expansion valve 16 is used to cool the HV device 31, the coolingperformance of air in the cabin in the heat exchanger 18 reduces and thecooling performance for cooling the cabin decreases. In contrast tothis, in the cooling system 1 according to the present embodiment, inthe vapor compression refrigeration cycle 10, high-pressure refrigerantdischarged from the compressor 12 is condensed by both the heatexchanger 14 that serves as a first condenser and the heat exchanger 15that serves as a second condenser. The two-stage heat exchangers 14 and15 are arranged between the compressor 12 and the expansion valve 16,and the cooling portion 30 for cooling the HV device 31 is providedbetween the heat exchanger 14 and the heat exchanger 15. The heatexchanger 15 is provided in the path of refrigerant flowing from thecooling portion 30 toward the expansion valve 16.

By sufficiently cooling refrigerant, which receives latent heat ofvaporization from the HV device 31 to be heated, in the heat exchanger15, the refrigerant has a temperature and a pressure that are originallyrequired to cool the cabin of the vehicle at the outlet of the expansionvalve 16. Therefore, it is possible to sufficiently increase the amountof heat externally received when refrigerant evaporates in the heatexchanger 18. Thus, by setting the heat radiation performance for theheat exchanger 15 so as to be able to sufficiently cool refrigerant, theHV device 31 may be cooled without any influence on the coolingperformance for cooling air in the cabin. Thus, both the coolingperformance for cooling the HV device 31 and the cooling performance forcooling the cabin may be reliably ensured.

When refrigerant flowing from the heat exchanger 14 to the coolingportion 30 cools the HV device 31, the refrigerant receives heat fromthe HV device 31 to be heated. As refrigerant is heated to a saturatedsteam temperature or above and the entire amount of the refrigerantvaporizes in the cooling portion 30, the amount of heat exchangedbetween the refrigerant and the HV device 31 reduces, and the HV device31 cannot be efficiently cooled, and, in addition, pressure loss at thetime when the refrigerant flows in the pipe increases. Therefore, it isdesirable to sufficiently cool refrigerant in the heat exchanger 14 suchthat the entire amount of refrigerant does not vaporize after coolingthe HV device 31.

Specifically, the state of refrigerant at the outlet of the heatexchanger 14 - is brought close to saturated liquid, and, typically,refrigerant is placed in a state on the saturated liquid line at theoutlet of the heat exchanger 14. Because the heat exchanger 14 iscapable of sufficiently cooling refrigerant in this way, the heatradiation performance of the heat exchanger 14 for causing refrigerantto release heat is higher than the heat radiation performance of theheat exchanger 15. By sufficiently cooling refrigerant in the heatexchanger 14 having relatively high heat radiation performance,refrigerant that has received heat from the HV device 31 may bemaintained in a wet steam state, and a reduction in the amount of heatexchanged between refrigerant and the HV device 31 may be avoided, so itis possible to sufficiently cool the HV device 31. Refrigerant in a wetsteam state after cooling the HV device 31 is efficiently cooled againin the heat exchanger 15, and is cooled into a supercooled liquid statebelow a saturated temperature. Thus, it is possible to provide thecooling system 1 that ensures both the cooling performance for coolingthe cabin and the cooling performance for cooing the HV device 31.

Referring back to FIG. 1, the refrigerant lines 23 and 24 and arefrigerant line 29 are connected in parallel in the path of refrigerantflowing between the heat exchanger 14 and the heat exchanger 15. Therefrigerant line 29 provides direct fluid communication between therefrigerant line 23 and the refrigerant line 24. The refrigerant line 29forms part of the path of refrigerant flowing between the heat exchanger14 and the heat exchanger 15. The cooling system 1 includes therefrigerant line 29 that forms the path that does not pass through thecooling portion 30, and the refrigerant lines 23 and 24 and the coolingline 32 that form the path that passes through the cooling portion 30.The path of refrigerant between the heat exchanger 14 and the heatexchanger 15 branches off, and part of refrigerant flows to the coolingportion 30.

The refrigerant lines 23 and 24 and the cooling line 32 that form thepath passing through the cooling portion 30 and the refrigerant line 29that forms the path not passing through the cooling portion 30 areprovided in parallel with each other as the path through whichrefrigerant flows between the heat exchanger 14 and the heat exchanger15. The cooling system for cooling the HV device 31, including therefrigerant lines 23 and 24, is connected in parallel with therefrigerant line 29. The path of refrigerant flowing between the heatexchanger 14 and the heat exchanger 15 without passing though thecooling portion 30 and the path of refrigerant flowing via the coolingportion 30 are provided in parallel with each other, and only part ofrefrigerant is caused to flow to the refrigerant lines 23 and 24. By sodoing, only part of refrigerant flowing between the heat exchanger 14and the heat exchanger 15 flows to the cooling portion 30.

Refrigerant in an amount required to cool the HV device 31 in thecooling portion 30 is caused to flow to the refrigerant lines 23 and 24,and not the entire refrigerant flows to the cooling portion 30. Thus,the HV device 31 is appropriately cooled, and it is possible to preventexcessive cooling of the HV device 31. In addition, it is possible toreduce the pressure loss associated with flow of refrigerant to thecooling system for cooling the HV device 31, including the refrigerantlines 23 and 24 and the cooling line 32. Accordingly, it is possible toreduce power consumption required to operate the compressor 12 forcirculating refrigerant.

A flow regulating valve 39 is provided in the refrigerant line 29. Theflow regulating valve 39 is arranged in the refrigerant line 29 thatforms part of the path of refrigerant flowing between the heat exchanger14 and the heat exchanger 15. The flow regulating valve 39 changes itsvalve opening degree to increase or reduce a pressure loss ofrefrigerant flowing in the refrigerant line 29 to thereby selectivelyadjust the flow rate of refrigerant flowing in the refrigerant line 29and the flow rate of refrigerant flowing in the cooling system forcooing the HV device 31, including the cooling line 32.

For example, as the flow regulating valve 39 is fully closed to set thevalve opening degree at 0%, the entire amount of refrigerant from theheat exchanger 14 flows into the cooling portion 30. When the valveopening degree of the flow regulating valve 39 is increased, the flowrate of refrigerant that flows directly to the heat exchanger 15 via therefrigerant line 29 increases and the flow rate of refrigerant thatflows to the cooling portion 30 to cool the HV device 31 reduces withinrefrigerant that flows from the heat exchanger 14 to the refrigerantline 23. When the valve opening degree of the flow regulating valve 39is reduced, the flow rate of refrigerant that directly flows to the heatexchanger 15 via the refrigerant line 29 reduces and the flow rate ofrefrigerant that flows to the cooling portion 30 to cool the HV device31 increases within refrigerant that flows from the heat exchanger 14 tothe refrigerant line 23.

As the valve opening degree of the flow regulating valve 39 isincreased, the flow rate of refrigerant that cools the HV device 31reduces, so cooling performance for cooling the HV device 31 decreases.As the valve opening degree of the flow regulating valve 39 reduces, theflow rate of refrigerant that cools the HV device 31 increases, socooling performance for cooling the HV device 31 improves. The flowregulating valve 39 is used to make it possible to optimally adjust theamount of refrigerant flowing to the HV device 31, so it is possible toreliably prevent excessive cooling of the HV device 31, and, inaddition, it is possible to reliably reduce pressure loss associatedwith flow of refrigerant in the cooling system for cooling the HV device31 and the power consumption of the compressor 12 for circulatingrefrigerant.

An example of control associated with adjustment of the valve openingdegree of the flow regulating valve 39 will be described below. FIG. 3Ato FIG. 3D are graphs that schematically show opening degree controlover the flow regulating valve 39. The abscissa axis shown in each ofthe graphs of FIG. 3A to FIG. 3D represents time.

The ordinate axis of the graph of FIG. 3A represents a valve openingdegree in the case where the flow regulating valve 39 is an electricexpansion valve that uses a stepping motor. The ordinate axis of thegraph of FIG. 3B represents a valve opening degree in the case where theflow regulating valve 39 is a thermostatic expansion valve that opens orcloses with a fluctuation in temperature. The ordinate axis of the graphof FIG. 3C represents the temperature of the HV device 31. The ordinateaxis of the graph of FIG. 3D represents a difference in temperaturebetween the inlet and outlet of the HV device 31.

As refrigerant flows via the cooling portion 30, the HV device 31 iscooled. The valve opening degree of the flow regulating valve 39 is, forexample, adjusted by monitoring the temperature of the HV device 31 orthe difference between the outlet temperature and inlet temperature ofthe HV device 31. For example, with reference to the graph of FIG. 3C, atemperature sensor that continuously measures the temperature of the HVdevice 31 is provided to monitor the temperature of the HV device 31. Inaddition, for example, with reference to the graph of FIG. 3D, atemperature sensor that measures the inlet temperature and outlettemperature of the HV device 31 is provided to monitor the difference intemperature between the outlet and inlet of the HV device 31.

As the temperature of the HV device 31 is higher than a targettemperature or the difference in temperature between the outlet andinlet of the HV device 31 is larger than a target temperature difference(for example, 3 to 5° C.), the opening degree of the flow regulatingvalve 39 is reduced as shown in the graph of FIG. 3A and the graph ofFIG. 3B. By throttling the opening degree of the flow regulating valve39, the flow rate of refrigerant flowing to the cooling portion 30increases as described above, so it is possible to further effectivelycool the HV device 31. As a result, the temperature of the HV device 31may be decreased to the target temperature or below as shown in thegraph of FIG. 3C or the different in temperature between the outlet andinlet of the HV device 31 may be reduced to the target temperaturedifference or below as shown in the graph of FIG. 3D.

In this way, by optimally adjusting the valve opening degree of the flowregulating valve 39, refrigerant in an amount by which heat radiationperformance required to keep the HV device 31 within an appropriatetemperature range is ensured is ensured to thereby make it possible toappropriately cool the HV device 31. Thus, it is possible to reliablysuppress occurrence of inconvenience that the HV device 31 isexcessively heated to be damaged.

FIG. 4 is a schematic view that shows the cooling system 1 in a statewhere the four-way valve 13 is switched. By comparing FIG. 4 with FIG.1, the four-way valve 13 is rotated by 90° to switch the path alongwhich refrigerant flowing from the outlet of the compressor 12 into thefour-way valve 13 flows out from the four-way valve 13. During coolingoperation shown in FIG. 1, refrigerant compressed in the compressor 12flows from the compressor 12 toward the heat exchanger 14. On the otherhand, during heating operation shown in FIG. 4, refrigerant compressedin the compressor 12 flows from the compressor 12 toward the heatexchanger 18.

During heating operation, refrigerant flows in the vapor compressionrefrigeration cycle 10 so as to sequentially pass through points A, B,H, G, F, E, D and C shown in FIG. 4 to circulate through the compressor12, the heat exchanger 18, the expansion valve 16 and the heatexchangers 15 and 14. Refrigerant passes through a refrigerantcirculation path that is formed by sequentially connecting thecompressor 12, the heat exchanger 18, the expansion valve 16 and theheat exchangers 15 and 14 by the refrigerant lines 21 to 28 to circulatein the vapor compression refrigeration cycle 10.

FIG. 5 is a Mollier chart that shows the state of refrigerant duringheating operation of the vapor compression refrigeration cycle 10according to the first embodiment. In FIG. 5, the abscissa axisrepresents the specific enthalpy (unit: kJ/kg) of refrigerant, and theordinate axis, represents the absolute pressure (unit: MPa) ofrefrigerant. The curve in the chart is the saturation vapor line andsaturation liquid line of refrigerant. FIG. 5 shows the thermodynamicstate of refrigerant at points (that is, points A, B, H, G, F, E, D andC) in the vapor compression refrigeration cycle 10 when refrigerantflows from the compressor 12 into the refrigerant line 24 via the heatexchanger 18, the expansion valve 16 and the heat exchanger 15, coolsthe HV device 31, and returns from the refrigerant line 23 to thecompressor 12 via the heat exchanger 14.

As shown in FIG. 5, refrigerant in a superheated steam state (point A),introduced into the compressor 12, is adiabatically compressed in thecompressor 12 along a constant specific entropy line. As refrigerant iscompressed, the refrigerant increases in pressure and temperature intohigh-temperature and high-pressure superheated steam having a highdegree of superheat (point B). Refrigerant flowing out from thecompressor 12 flows to the internal heat exchanger 40. As heat istransferred from refrigerant that flows through the heat exchanging line42 to refrigerant that flows through the heat exchanging line 41 insidethe internal heat exchanger 40, refrigerant that flows through the heatexchanging line 42 is cooled, and refrigerant that flows through theheat exchanging line 41 is heated. By heat exchange in the internal heatexchanger 40, a degree of superheat of refrigerant that flows throughthe heat exchanging line 42 reduces. That is, the temperature ofrefrigerant in a superheated steam state decreases, and approaches asaturated temperature of refrigerant steam (point H).

After that, refrigerant flows to the heat exchanger 18. High-pressurerefrigerant steam in the heat exchanger 18 is cooled in the heatexchanger 18, becomes dry saturated steam from superheated steam with aconstant pressure, releases latent heat of condensation to graduallyliquefy into wet steam in a gas-liquid mixing state, becomes saturatedliquid as the entire refrigerant condenses, and further releasessensible heat to become supercooled liquid (point G). The heat exchanger18 causes superheated refrigerant gas, compressed in the compressor 12,to release heat to an external medium with a constant pressure and tobecome refrigerant liquid. Gaseous refrigerant discharged from thecompressor 12 releases heat to the surroundings to be cooled in the heatexchanger 18 to thereby condense (liquefy). Owing to heat exchange inthe heat exchanger 18, the temperature of refrigerant decreases, andrefrigerant liquefies. Refrigerant releases heat to the surroundings inthe heat exchanger 18 to be cooled.

High-pressure liquid refrigerant liquefied in the heat exchanger 18flows into the expansion valve 16 via the refrigerant line 26. In theexpansion valve 16, refrigerant in a supercooled liquid state isthrottle-expanded, and the refrigerant decreases in temperature andpressure with the specific enthalpy of the refrigerant unchanged tobecome low-temperature and low-pressure wet steam in a gas-liquid mixingstate (point F). Refrigerant of which the temperature is decreased inthe expansion valve 16 flows into the heat exchanger 15 via therefrigerant line 25. Refrigerant in a wet steam state flows into thetubes of the heat exchanger 15. When refrigerant flows through thetubes, the refrigerant absorbs heat of outside air via the fins aslatent heat of vaporization to evaporate with a constant pressure.Refrigerant exchanges heat with outside air in the heat exchanger 15 tobe heated, and the dryness of the refrigerant increases. Part ofrefrigerant receives latent heat in the heat exchanger 15 to vaporize,so the percentage of saturated steam contained in the refrigerant in awet steam state increases (point E).

Refrigerant in a wet steam state, flowing out from the heat exchanger15, flows to the internal heat exchanger 40 via the refrigerant line 24b and flows through the heat exchanging line 41. By the above describedheat exchange in the internal heat exchanger 40, refrigerant that flowsthrough the heat exchanging line 41 is heated, and the dryness of therefrigerant in a wet steam state, flowing through the heat exchangingline 41, increases (point D). Next, refrigerant flows to the coolingline 32 of the cooling portion 30 to cool the HV device 31. Refrigerantis heated by exchanging heat with the HV device 31, and the dryness ofthe refrigerant increases. Part of refrigerant receives latent heat fromthe HV device 31 to vaporize, so the percentage of saturated steamcontained in the refrigerant in a wet steam state increases (point C).

Refrigerant in a wet steam state, flowing out from the cooling portion30, flows into the heat exchanger 14 via the refrigerant line 23.Refrigerant in a wet steam state flows into the tubes of the heatexchanger 14. When refrigerant flows through the tubes, the refrigerantabsorbs heat of outside air via the fins as latent heat of vaporizationto evaporate with a constant pressure. As the entire refrigerant becomesdry saturated steam, the refrigerant steam further increases intemperature by sensible heat to become superheated steam (point A).Vaporized refrigerant is introduced into the compressor 12 via therefrigerant line 22. The compressor 12 compresses refrigerant flowingfrom the heat exchanger 14. Refrigerant continuously repeats changesamong the compressed state, the condensed state, the throttle-expandedstate and the evaporated state in accordance with the above describedcycle.

During heating operation, refrigerant steam flowing inside the heatexchanger 18 condenses to release heat to ambient air introduced so asto contact with the heat exchanger 18. The heat exchanger 18 useshigh-temperature and high-pressure refrigerant adiabatically compressedin the compressor 12 to release heat of condensation, required at thetime when refrigerant gas condenses into wet steam of refrigerant, toair-conditioning air flowing to the cabin of the vehicle to thereby heatthe cabin of the vehicle. Air-conditioning air that receives heat fromthe heat exchanger 18 to increase its temperature flows into the cabinof the vehicle to thereby heat the cabin of the vehicle.

During operation of the vapor compression refrigeration cycle 10,refrigerant releases heat of condensation to air in the cabin of thevehicle in the heat exchanger 18 to thereby heat the cabin. In addition,refrigerant in a wet steam state, flowing out from the heat exchanger15, flows to the cooling portion 30 and exchanges heat with the HVdevice 31 to thereby cool the HV device 31. During heating as well, asin the case during cooling, the cooling system 1 utilizes the vaporcompression refrigeration cycle 10 for air-conditioning the cabin of thevehicle to thereby cool the HV device 31.

The four-way valve 13 is used to switch the direction in whichrefrigerant flows in the vapor compression refrigeration cycle 10between cooling operation and heating operation. During coolingoperation, in the heat exchanger 18, low-temperature and low-pressurerefrigerant throttle-expanded in the expansion valve 16 absorbs heatfrom air-conditioning air to cool the cabin. During heating operation,in the heat exchanger 18, high-temperature and high-pressure refrigerantadiabatically compressed in the compressor 12 releases heat toair-conditioning air to heat the cabin. The cooling system 1 uses thesingle heat exchanger 18 to be able to appropriately adjust thetemperature of air-conditioning air flowing into the cabin of thevehicle during both cooling operation and heating operation. Thus, it isnot required to arrange two heat exchangers that exchange heat withair-conditioning air, so the cost of the cooling system 1 may bereduced, and the size of the cooling system 1 may be reduced.

During both cooling operation and heating operation, refrigerant flowsto the cooling portion 30 to exchange heat with the HV device 31 tothereby cool the HV device 31. The cooling system 1 cools the HV device31, which is the heat generating source mounted on the vehicle, byutilizing the vapor compression refrigeration cycle 10 forair-conditioning the cabin of the vehicle. The vapor compressionrefrigeration cycle 10 that is provided in order to exchange heat withair-conditioning air in the heat exchanger 18 to air-condition the cabinof the vehicle is utilized to cool the HV device 31.

It is not necessary to provide a device, such as an exclusive watercirculation pump and a cooling fan, in order to cool the HV device 31.Therefore, components required for the cooling system 1 to cool the HVdevice 31 may be reduced to make it possible to simplify the systemconfiguration, so the manufacturing cost of the cooling system 1 may bereduced. In addition, it is not necessary to operate a power source,such as a pump and a cooling fan, in order to cool the HV device 31, andpower consumption for operating the power source is not required. Thus,it is possible to reduce power consumption for cooling the HV device 31.

As shown in FIG. 1 and FIG. 4, the cooling system 1 according to thepresent embodiment further includes a communication line 51 that servesas a fourth line. The communication line 51 provides fluid communicationbetween the refrigerant line 22 that serves as a third line, throughwhich refrigerant flows between the compressor 12 and the heat exchanger14, and the refrigerant line 24 (24 b) that serves as the first line. Aselector valve 52 is provided in the refrigerant line 24 and thecommunication line 51. The selector valve 52 switches the state of fluidcommunication between the communication line 51 and the refrigerantlines 24 and 22. The selector valve 52 switches between the open stateand the closed state to thereby allow or interrupt flow of refrigerantvia the communication line 51. By switching the path of refrigerantusing the selector valve 52, refrigerant after cooling the HV device 31may be caused to flow to any selected one of the paths, that is, to theheat exchanger 15 via the refrigerant line 24 or to the heat exchanger14 via the communication line 51 and the refrigerant line 22.

More specifically, two valves 57 and 58 are provided as the selectorvalve 52. During cooling operation of the vapor compressionrefrigeration cycle 10, the valve 57 is fully open (valve opening degree100%) and the valve 58 is fully closed (valve opening degree 0%), andthe valve opening degree of the flow regulating valve 39 is adjustedsuch that a sufficient amount of refrigerant flows through the coolingportion 30. By so doing, refrigerant after cooling the HV device 31 maybe reliably caused to flow to the heat exchanger 15 via the refrigerantline 24. On the other hand, during a stop of the vapor compressionrefrigeration cycle 10, the valve 58 is fully open and the valve 57 isfully closed, and, furthermore, the flow regulating valve 39 is fullyclosed. By so doing, it is possible to form an annular path that causesrefrigerant to circulate between the cooling portion 30 and the heatexchanger 14.

FIG. 6 is a schematic view that shows flow of refrigerant that cools theHV device 31 during cooling operation of the vapor compressionrefrigeration cycle 10. When the compressor 12 is driven and the vaporcompression refrigeration cycle 10 is operated, the flow regulatingvalve 39 is adjusted in valve opening degree such that a sufficientamount of refrigerant flows through the cooling portion 30. The selectorvalve 52 is operated so as to flow refrigerant from the cooling portion30 to the expansion valve 16 via the heat exchanger 15. That is, as thevalve 57 is fully open and the valve 58 is fully closed, the path ofrefrigerant that causes refrigerant to flow the whole of the coolingsystem 1 is selected. Therefore, the cooling performance of the vaporcompression refrigeration cycle 10 may be ensured, and the HV device 31may be efficiently cooled.

FIG. 7 is a schematic view that shows flow of refrigerant that cools theHV device 31 during a stop of the vapor compression refrigeration cycle10. As shown in FIG. 7, when the compressor 12 is stopped and the vaporcompression refrigeration cycle 10 is stopped, the selector valve 52 isoperated so as to circulate refrigerant from the cooling portion 30 tothe heat exchanger 14. That is, as the valve 57 is fully closed, thevalve 58 is fully open and the flow regulating valve 39 is fully closed,refrigerant flows via the communication line 51. By so doing, a closedannular path that is routed from the heat exchanger 14 to the coolingportion 30 via the refrigerant line 23, further passes through therefrigerant line 24, the communication line 51 and the refrigerant line22 sequentially and returns to the heat exchanger 14 is formed.

Refrigerant may be circulated between the heat exchanger 14 and thecooling portion 30 via the annular path without operating the compressor12. When refrigerant cools the HV device 31, the refrigerant receiveslatent heat of vaporization from the HV device 31 to evaporate.Refrigerant steam vaporized by exchanging heat with the HV device 31flows to the heat exchanger 14 via the refrigerant line 24, thecommunication line 51 and the refrigerant line 22 sequentially. In theheat exchanger 14, refrigerant steam is cooled to condense by runningwind of the vehicle or draft from a radiator fan for cooling an engine.Refrigerant liquid liquefied in the heat exchanger 14 returns to thecooling portion 30 via the refrigerant line 23.

In this way, a heat pipe in which the HV device 31 serves as a heatingportion and the heat exchanger 14 serves as a cooling portion is formedby the annular path that passes through the cooling portion 30 and theheat exchanger 14. Thus, when the vapor compression refrigeration cycle10 is stopped, that is, when a cooler for the vehicle is stopped aswell, the HV device 31 may be reliably cooled without the necessity ofstart-up of the compressor 12. Because the compressor 12 is not requiredto constantly operate in order to cool the HV device 31, the powerconsumption of the compressor 12 is reduced to thereby make it possibleto improve the fuel economy of the vehicle and, in addition, to extendthe life of the compressor 12, so it is possible to improve thereliability of the compressor 12.

FIG. 6 and FIG. 7 show a ground 60. The cooling portion 30 is arrangedbelow the heat exchanger 14 in the vertical direction perpendicular tothe ground 60. In the annular path that circulates refrigerant betweenthe heat exchanger 14 and the cooling portion 30, the cooling portion 30is arranged below, and the heat exchanger 14 is arranged above. The heatexchanger 14 is arranged at the level higher than the cooling portion30.

In this case, refrigerant steam heated and vaporized in the coolingportion 30 goes up in the annular path, reaches the heat exchanger 14,is cooled in the heat exchanger 14, condenses into liquid refrigerant,goes down in the annular path by the action of gravity and returns tothe cooling portion 30. That is, a thermo-siphon heat pipe is formed ofthe cooling portion 30, the heat exchanger 14 and the paths ofrefrigerant that connect them. Because the heat transfer efficiency fromthe HV device 31 to the heat exchanger 14 may be improved by forming theheat pipe, when the vapor compression refrigeration cycle 10 is stoppedas well, the HV device 31 may be further efficiently cooled withoutadditional power.

The selector valve 52 that switches the state of fluid communicationbetween the communication line 51 and the refrigerant lines 24 and 22may be the above described pair of valves 57 and 58 or may be athree-way valve that is arranged at the branching portion between therefrigerant line 24 and the communication line 51. In any cases, duringboth operation and stop of the vapor compression refrigeration cycle 10,the HV device 31 may be efficiently cooled. The valves 57 and 58 justneed to have a simple structure so as to be able to open or close therefrigerant line, so the valves 57 and 58 are not expensive, and the twovalves 57 and 58 are used to make it possible to provide the furtherlow-cost cooling system 1. On the other hand, it is presumable that aspace required to arrange the three-way valve is smaller than a spacerequired to arrange the two valves 57 and 58, and the three-way valve isused to make it possible to provide the cooling system 1 having afurther reduced size and excellent vehicle mountability.

As described above, in the cooling system 1 according to the presentembodiment, refrigerant after cooling the HV device 31 in the coolingportion 30 and refrigerant after exchanging heat with air, used for thecabin, in the heat exchanger 18 exchange heat with each other in theinternal heat exchanger 40. By so doing, during cooling operation,refrigerant heated by exchanging heat with the HV device 31 is cooled inthe internal heat exchanger 40. Therefore, refrigerant after passingthrough the heat exchanger 15 may be cooled into a supercooled liquidstate without increasing the capacity of the heat exchanger 15, so thesize of the heat exchanger 15 may be reduced. When the amount of heatgenerated by the HV device 31 is small, a degree of supercooling ofrefrigerant increases, so the cooling performance may be improved. Inthis case, additionally, the power of the compressor 12 may be reduced,so power saving of the cooling system 1 may be achieved. When the amountof heat generated by the HV device 31 is large as well, the coolingsystem 1 is controlled such that refrigerant is reliably cooled into asupercooled liquid state, so controllability of cooling operation may beimproved.

During heating operation, refrigerant absorbs heat from outside air tobe heated in the heat exchangers 15 and 14. Refrigerant is additionallyheated in the internal heat exchanger 40 as well, and absorbs heat fromthe HV device 31 to be further heated in the cooling portion 30. Becauserefrigerant is heated not only in the heat exchangers 15 and 14 but alsoin the internal heat exchanger 40 and the cooling portion 30, therefrigerant may be heated into a sufficient superheated steam state atthe outlet of the heat exchanger 14, so the HV device 31 may beappropriately cooled while maintaining excellent heating performance inthe cabin of the vehicle.

Therefore, refrigerant after passing through the heat exchanger 14 maybe heated into a superheated steam state without increasing thecapacities of the heat exchangers 15 and 14, so the size of each of theheat exchangers 14 and 15 may be reduced. Refrigerant is heated in thecooling portion 30 and heat waste from the HV device 31 may beeffectively utilized to heat the cabin, so the coefficient ofperformance improves, and the power consumption for adiabaticallycompressing refrigerant in the compressor 12 during heating operationmay be reduced.

Second Embodiment

FIG. 8 is a schematic view that shows the configuration of a coolingsystem 1 according to a second embodiment. The cooling system 1according to the second embodiment differs from the cooling system 1according to the first embodiment in that the heat exchanger 14 and theheat exchanger 15 are manufactured as an integrated heat exchanger.

FIG. 9 is a schematic view that shows an example of the internalstructure of the heat exchangers 14 and 15 according to the secondembodiment. As shown in FIG. 9, the heat exchanger 14 and the heatexchanger 15 are integrally arranged. The integrally arranged heatexchanger 14 and heat exchanger 15 are, for example, provided next to anengine cooling radiator mounted on the vehicle, and carries out heatexchange between running wind of the vehicle or cooling air supplied bya cooling fan and refrigerant.

The heat exchanger 14 includes a plurality of tubes 146 through whichrefrigerant flows and a plurality of fins 148 that are used to exchangeheat between refrigerant in the plurality of tubes 146 and air aroundthe heat exchanger 14. The plurality of tubes 146 are arranged inparallel with one another between an inlet portion 142 and an outletportion 144. The inlet portion 142 is connected to the refrigerant line22, and introduces refrigerant from the compressor 12. The outletportion 144 is connected to the refrigerant line 23 routed to thecooling portion 30. Refrigerant introduced via the inlet portion 142flows through the plurality of tubes 146 in a distributed manner.

Each of the plurality of fins 148 are arranged next to the gap betweenany adjacent two of the plurality of tubes 146 between the inlet portion142 and the outlet portion 144. Refrigerant exchanges heat with airaround the heat exchanger 14 via the fin 148 to be condensed in each ofthe plurality of tubes 146. Refrigerant after being condensed in theheat exchanger 14 flows from the outlet portion 144 to the coolingportion 30.

The heat exchanger 15 includes a plurality of tubes 156 and fins 158.The plurality of tubes 156 flow refrigerant. The fins 158 are used toexchange heat between refrigerant in the plurality of tubes 156 and airaround the heat exchanger 15. The plurality of tubes 156 are arranged inparallel with one another between an inlet portion 152 and an outletportion 154. The inlet portion 152 is connected to the refrigerant line24, and introduces refrigerant from the cooling portion 30. The outletportion 154 is connected to the refrigerant line 25 routed to theexpansion valve 16. Refrigerant introduced via the inlet portion 152flows through the plurality of tubes 156 in a distributed manner.

Each of the plurality of fins 158 is arranged next to the gap betweenany adjacent two of the plurality of tubes 156 between the inlet portion152 and the outlet portion 154. Refrigerant is cooled by exchanging heatwith air around the heat exchanger 15 via the fin 158 in each of theplurality of tubes 156. Refrigerant after being cooled in the heatexchanger 15 flows from the outlet portion 154 to the heat exchanger 18via the expansion valve 16.

As shown in FIG. 9, a partition and individual outlets and inlets areprovided for the integrated heat exchanger to thereby make it possibleto cause the integrated heat exchanger to separately serve as the twoheat exchangers 14 and 15, so manufacturing cost of the heat exchangers14 and 15 may be reduced.

The cooling system 1 according to the second embodiment further includesa check valve 54. The check valve 54 is arranged in the refrigerant line22 between the compressor 12 and the heat exchanger 14 on the sidecloser to the compressor 12 than the connection portion between therefrigerant line 22 and the communication line 51. The check valve 54allows flow of refrigerant from the compressor 12 toward the heatexchanger 14 and prohibits flow of refrigerant in the oppositedirection.

By so doing, when the flow regulating valve 39 is fully closed (valveopening degree 0%) and the selector valve 52 is adjusted such thatrefrigerant flows from the refrigerant line 24 to the communication line51 and does not flow to the heat exchanger 15, a closed loop path ofrefrigerant for circulating refrigerant between the heat exchanger 14and the cooling portion 30 may be reliably formed.

When no check valve 54 is provided, refrigerant may flow from thecommunication line 51 to the refrigerant line 22 adjacent to thecompressor 12. By providing the check valve 54, it is possible toreliably prohibit flow of refrigerant from the communication line 51toward the side adjacent to the compressor 12, so it is possible toprevent a decrease in the cooling performance for cooling the HV device31 during a stop of the vapor compression refrigeration cycle 10, usingthe heat pipe that forms the annular refrigerant path. Thus, when thecooler for the cabin of the vehicle is, stopped as well, it is possibleto efficiently cool the HV device 31.

In addition, when the amount of refrigerant in the closed loop path ofrefrigerant is insufficient during a stop of the vapor compressionrefrigeration cycle 10, the compressor 12 is operated only in a shortperiod of time to thereby make it possible to supply refrigerant to theclosed loop path via the check valve 54. By so doing, the amount ofrefrigerant in the closed loop may be increased to thereby increase theamount of heat exchanged in the heat pipe. Thus, the amount ofrefrigerant in the heat pipe may be ensured, so it is possible to avoidinsufficient cooling of the HV device 31 because of an insufficientamount of refrigerant.

The cooling system 1 according to the second embodiment further includesa gas-liquid separator 70. Refrigerant flowing out from the heatexchanger 14 is separated into gas and liquid in the gas-liquidseparator 70. Liquid refrigerant separated in the gas-liquid separator70 flows via the refrigerant line 23 and is supplied to the coolingportion 30 to cool the HV device 31. The liquid refrigerant isrefrigerant in a just saturated liquid state. By taking only liquidrefrigerant from the gas-liquid separator 70 and flowing the liquidrefrigerant to the cooling portion 30, the performance of the heatexchanger 14 may be fully utilized to cool the HV device 31, so it ispossible to provide the cooling system 1 having improved coolingperformance for cooling the HV device 31.

Refrigerant in a saturated liquid state at the outlet of the gas-liquidseparator 70 is introduced into the cooling line 32 that cools the HVdevice 31 to thereby make it possible to minimize gaseous refrigerantwithin refrigerant that flows in the cooling system for cooling the HVdevice 31, including the refrigerant lines 23 and 24 and the coolingline 32. Therefore, it is possible to suppress an increase in pressureloss due to an increase in flow rate of refrigerant steam flowing in thecooling system of the HV device 31, and the power consumption of thecompressor 12 for flowing refrigerant may be reduced, so it is possibleto avoid deterioration of the performance of the vapor compressionrefrigeration cycle 10.

Refrigerant liquid in a saturated liquid state is stored inside thegas-liquid separator 70 as shown in FIG. 8. The gas-liquid separator 70functions as a reservoir that temporarily stores refrigerant liquidinside. When refrigerant liquid in a predetermined amount is stored inthe gas-liquid separator 70, the flow rate of refrigerant flowing fromthe gas-liquid separator 70 to the cooling portion 30 may be maintainedat the time of fluctuations in load. Because the gas-liquid separator 70has the function of storing liquid, serves as a buffer against loadfluctuations and is able to absorb load fluctuations, the coolingperformance for cooling the HV device 31 may be stabilized.

Note that, in the above described embodiments, the cooling system 1 thatcools an electrical device mounted on the vehicle is described using theHV device 31 as an example. The electrical device is not limited to theillustrated electrical devices, such as an inverter and a motorgenerator. The electrical device may be any electrical device as long asit generates heat when it is operated. In the case where there are aplurality of electrical devices to be cooled, the plurality ofelectrical devices desirably have a common cooling target temperaturerange. The target temperature range for cooling is an appropriatetemperature range as a temperature environment in which the electricaldevices are operated.

Furthermore, the heat generating source cooled by the cooling system 1according to the embodiments of the invention is not limited to theelectrical device mounted on the vehicle; instead, it may be any devicethat generates heat or may be a heat generating portion of any device.

The embodiments of the invention are described above; however, theconfigurations of the embodiments may be combined where appropriate. Inaddition, the embodiments described above should be regarded as onlyillustrative in every respect and not restrictive. The scope of theinvention is indicated not by the above description but by the appendedclaims, and is intended to include all modifications within the meaningand scope equivalent to the scope of the appended claims.

The cooling system according to the aspect of the invention may beparticularly advantageously applied to cooling of an electrical device,such as a motor generator and an inverter, using a vapor compressionrefrigeration cycle for cooling and heating a cabin, in a vehicle, suchas a hybrid vehicle, a fuel-cell vehicle and an electric vehicle,equipped with the electrical device.

1. A cooling system for cooling a heat generating source, comprising: acompressor configured to circulate refrigerant; a first heat exchangerand a second heat exchanger configured to carry out heat exchangebetween the refrigerant and outside air; a decompressor configured todecompress the refrigerant; a third heat exchanger configured to carryout heat exchange between the refrigerant and air-conditioning air; acooling portion provided in a path of the refrigerant flowing betweenthe first heat exchanger and the second heat exchanger, the coolingportion configured to use the refrigerant to cool the heat generatingsource; a first line through which the refrigerant flows between thecooling portion and the second heat exchanger; a second line throughwhich the refrigerant flows between the third heat exchanger and thecompressor; and an internal heat exchanger in which the refrigerant thatflows through the first line and the refrigerant that flows through thesecond line exchange heat with each other.
 2. The cooling systemaccording to claim 1, wherein the internal heat exchanger is arrangedbetween the cooling portion and the second heat exchanger.
 3. Thecooling system according to claim 1, further comprising: a third linethrough which the refrigerant flows between the compressor and the firstheat exchanger; and a fourth line configured to provide fluidcommunication between the first line and the third line.
 4. The coolingsystem according to claim 3, further comprising: a selector valveconfigured to switch a state of fluid communication between the fourthline, and the first line and the third line.
 5. The cooling systemaccording to claim 4, wherein the selector valve is configured so as toswitch the state of fluid communication into a state where therefrigerant flows through the fourth line during a stop of thecompressor.
 6. The cooling system according to claim 3, wherein thecooling portion is arranged below the first heat exchanger.
 7. Thecooling system according to claim 1, further comprising: a four-wayvalve configured to switch between flow of the refrigerant from thecompressor toward the first heat exchanger and flow of the refrigerantfrom the compressor toward the third heat exchanger.
 8. The coolingsystem according to claim 1, wherein the first heat exchanger and thesecond heat exchanger are integrally arranged.